Recently, as an electrophoresis device, a capillary electrophoresis device in which capillaries are filled with a phoretic medium such as polymer gel or polymer solution has been widely used.
For example, a capillary electrophoresis device as disclosed in PTL 1 has been used from the related art. Since the capillary electrophoresis device has higher heat-radiation properties than that of a flat plate type electrophoresis device, and a higher voltage can be applied to a sample, there is an advantage that electrophoresis is able to be performed at high speed. In addition, there are lots of advantages that, for example, a small amount of the sample is enough to complete an analysis, or automatic filling of the phoretic medium or sample automatic injection can be performed, and the capillary electrophoresis device is used for various separation analysis measurements as well as analysis of nucleic acid or protein.
In PTL 1, filling of the phoretic medium is performed using a syringe pump. There is a relay flow passage block having a function of the syringe pump, and filling is performed by connecting capillaries, sucking the phoretic medium using the syringe pump, and discharging the phoretic medium to the capillaries. In addition to the relay flow passage block, a buffer solution for performing electrophoresis is also connected, and the flow passage is switched by opening and closing a valve inside the relay flow passage block.
In the capillary electrophoresis device, the phoretic medium container or the capillaries are required to be replaced. However, at the time of replacing this component, since a part of the relay flow passage block is exposed to air, there is a possibility that air is mixed into the flow passage. At the time of performing the electrophoresis, a high voltage of several to several tens of kV is applied between both ends of the flow passage. Therefore, in a case in which bubbles are present inside the flow passage, there is a possibility that the flow passage is electrically blocked due to the bubbles. In a case in which the flow passage is electrically blocked, a high voltage difference occurs at the blocked part so as to cause electric discharge. According to magnitude of the electric discharge, there is a possibility that the capillary electrophoresis device is destroyed. Accordingly, before starting the electrophoresis, the bubbles need to be removed from the inside of the flow passage.
For example, in a case in which bubbles are present inside the flow passage of the relay flow passage block, a valve of the flow passage connected with the buffer solution is opened, and the phoretic medium is allowed to flow to the buffer solution side. Accordingly, the bubbles are removed from a section of flow passage inside the relay flow passage block. Meanwhile, in a case in which the bubbles are present in the flow passage of the capillaries, the inside of the capillaries are filled with the phoretic medium in an amount approximately twice with respect to a volume inside the capillaries. At this time, an inner diameter of each of the capillaries is as thin as approximately 50 μm. Therefore, the bubbles flow inside the capillaries with the phoretic medium, and are discharged from the other end of the capillaries. That is, the bubbles can be removed from the insides of the capillaries.
Filling of the phoretic medium to the capillaries can be performed by the same method as that of the related art. However, in a filling method of the phoretic medium, the extra phoretic medium is required to remove bubbles, such that the extra thereof becomes wasted. In a case in which analysis is performed many times at once, since the bubbles are removed only once, an amount of the wasted phoretic medium is small, but in a case in which the analysis is performed for less times at once, the bubbles are required to be removed whenever the capillaries or the phoretic medium are connected, and the amount of the wasted phoretic medium per the number of analyses increases. Since the phoretic medium is expensive, the amount of the wasted phoretic medium increases, and thus running costs thereof increase. In addition, if the electrophoresis is performed in a state in which the bubbles are remained, there is a possibility that the relay flow passage block is damaged. In this case, a damaged part is required to be repaired, and thus it takes a lot of time until restarting the inspection. Therefore, a user needs to check the presence and absence of the bubbles.
PTL 2 illustrates a structure in which bubbles in a relay flow passage block are not required to be visually checked and a difficulty of operating an electrophoresis device is reduced. Specifically, a phoretic medium container is set to a disposable phoretic medium container provided with a liquid feeding mechanism, and capillaries and flow passages of a phoretic medium and a buffer solution are switched in a detachable manner. Only in a case in which the phoretic medium is filled, the phoretic medium container and the capillaries are connected, at the time of performing the electrophoresis, the capillaries are detached from the phoretic medium container, and both ends of each of the capillaries are directly soaked into the buffer solution. That is, the relay flow passage block itself is not needed. Accordingly, the amount of the wasted phoretic medium for removing the bubbles is reduced, a flow passage having a risk of mixing of bubbles at the time of performing the electrophoresis can be removed, and thus the previous visual checking of bubbles by the user before performing the electrophoresis can be omitted. Even if the electrophoresis is performed in a state in which the bubbles are remained inside the flow passage, the damaged part can be limited to the capillaries. Also, since the capillaries are articles of consumption, it does not need to be repaired like the relay flow passage block. That is, the inspection can be restarted only by replacing the capillaries. Therefore, the time required until restarting the inspection can be significantly shortened.